With the advances in recent automobile technology, several new technologies have been proposed for improving the driving characteristics such as 4-wheel steering (4WS), 4-wheel driving (4WD), anti-skid brake system (ABS) and traction control.
However, these new technologies are concerned with handling the driving force of each front and rear wheel. Therefore, in order to carry out the above-mentioned new automobile technologies, it is necessary to control each wheel properly, (based upon the necessary conditions) by adding new mechanical structures to the automobile structures of the prior art.
In general, an automobile is provided with steering wheels for changing the traveling direction of the vehicle and driving wheels for driving the vehicle. Recently, for improving vehicle driving characteristics and for securing a sufficient inside vehicle space, a front-drive (and a 4WD) vehicle has been widely used in which steering wheels also function as driving wheels.
A conventional vehicle usually uses a driving system in which the power from a single power source (an engine) is divided into plural driving wheels. Accordingly, new mechanisms, which are added to carry out the above new technologies, as well as the resulting mechanical structure into which the new mechanisms are incorporated, tend to complicate the mechanical structure of the vehicle because of the driving system. This is the same case for an electric vehicle.
In the case where the steering wheels not only have a steering function but also a driving function, it is necessary not only to swivel each of the steering wheels about its king pin shaft, but also to impart the driving force to each of the steering wheels. Accordingly, the mechanical structure for performing both the steering and driving functions becomes very complicated.
It is therefore a main object to improve the driving characteristics of an electric vehicle and to provide an electric vehicle having a simple mechanical structure easily carrying out the new technologies mentioned above.
It is a second object to improve the driving characteristics of an electric vehicle by simplifying the structure of steering wheels which have both steering and driving functions and by increasing the degree of freedom of the swiveling motion of steering wheels.